MTP3 API Operation
1. Sample application
Note: Not implemented yetÂ
The sample application is a good way to get familiar with the FreeTDM interface.Â
After generating your sample /usr/local/freetdm/conf/freetdm.conf and freetdm.conf.xml files, Â you can run the sample application:
#>./run_mtp3 -conf freetdm.conf.xml
The sample application will transmit dummy MSU's on each MTP3 link. And listen incoming events from FreeTDM. The source codes for the run_mtp2 application are:
run_mtp3.c
Initialization and configuration.Ârun_mtp3_test.c
Test functions and event handlers.Â
2. Initialization
The FreeTDM library is initialised using the following function calls:
ftdm_global_init()
ftdm_global_configuration()
For each span:
ftdm_configue_span_signaling(...);For each span:
ftdm_span_start(...);Â
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2.1 ftdm_global_init(void)
FreeTDM initialization function. FreeTDM internal variables and parameters are initialized when this function is called.
2.2. ftdm_global_configuration(void)
FreeTDM general configuration function. FreeTDM protocol specific modules are initialized and loaded when this function is called.
2.3.ftdm_configure_span_signaling(ftdm_span_t *span, fio_signal_cb_t sig_cb, ftdm_conf_parameter_t *ftdm_parameters)
Signaling parameters for each span are set using this function.
span:Â FreeTDM span structure.
sig_cb:Â Call back function for events.
ftdm_parameters:Â configuration parameters. Refer to run_mtp2.c:load_config function for an example of how ftdm_parameters is populated.
2.4.ftdm_span_start(ftdm_span_t *span);
Starts the span. Â
3. API Requests
3.1. ftdm_status_t ftdm_channel_set_sig_status_ex(ftdm_channel_t *ftdmchan, ftdm_signaling_status_t sigstatus, ftdm_usrmsg_t *usrmsg);
This function is used by the upper layer to request a change of status to MTP3.
TBD
3.2. ftdm_channel_call_indicate_ex(ftdm_channel_t *ftdmchan, ftdm_channel_indication_t indication, ftdm_usrmsg_t *usrmsg);
This function is used by the upper layer to request maintenance tasks to MTP3.
3.3. ftdm_channel_write(ftdm_channel_t *ftdmchan, void* data, ftdm_size_t datasize, ftdm_size_t datalen);Â
Used to transmit MSU's.Â
example:
/* Request MTP3 to transmit */
static void request_mtp3_transmit(ftdm_channel_t *ftdmchan, void* data, uint32_t datalen)
{
if (ftdm_channel_write(ftdmchan, data, MAX_MSU_SIZE, &datalen) != FTDM_SUCCESS) {
fprintf(stderr, "Failed to write data to channel\n");
}
return;
}
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4. API EventsÂ
All indications from the MTP2 layer will result in a signal callback function that was previously registered using ftdm_span_configure.
event_id | Event Type |
FTDM_SIGEVENT_SIGSTATUS_CHANGED | Signalling status changed |
FTDM_SIGEVENT_RAW | Response to a maintenance request |
FTDM_SIGEVENT_IO_INDATA | Incoming data received |
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 To be finalized:
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User application will be able to register multiple callback function for incoming data, for example:
User application will register 1 callback function for incoming ISUP messages, and 1 callback function for  SCCP messages. When an incoming ISUP message is received, the callback function for ISUP will be called, and when a SCCP message is received, the callback function for SCCP will be called.